Various types of dishwashers have been utilized in the domestic and commercial industries. The technology used to operate the dishwashers has largely remained consistent over the past few years. Although dishwashers vary in size and shape, their function is consistent; dishes inside the dishwasher are cleaned by water which is heated to sanitizing temperatures. Dishwashers may also include an option to add detergents to the wash cycle as well as an option to add a drying cycle at the end of the wash cycle.
Typically, a dishwasher has a tub with an interior surface and an exterior surface. Water is supplied to and removed from the interior surface of the tub by a pump assembly. The water may be supplied through a manifold that vents to the inside of the tub. The water supplied is heated to a pre-determined sanitizing temperature by utilizing either an in line heater within the pump assembly or a heating element disposed inside the tub. For example, in many traditional dishwashers, the heating element is a heating coil. The heating element may also be utilized to heat the air inside the tub, which also assists in the drying of contents within the tub.
Appliances, such as dishwashers, washers, dryers and other machines that generate noise are usually provided with acoustical insulation to reduce the levels of sound emanating from the machines. The unwanted sound from these machines can be caused both by the mechanical operation of the motor within the machine and by the vibration of the machine itself. In a residential dwelling, excessive noise may be generated by dishwashers, clothes washers and clothes dryers, which can be annoying to inhabitants of the dwelling.
Conventional acoustical treatments for machines generally comprises sound transmission barriers and sound absorption layers. One form of acoustical insulation involves enclosing the noise source in an insulation structure. A typical form of acoustical insulation is a layer of mineral fiber insulation, such as fiberglass insulation, wrapped around or positioned around the source of unwanted noise. For example, a fiberglass absorber is usually incorporated in the front door panel of an under-the-counter dishwasher. The blanket of glass fibers absorbs some of the sound energy entering the fiberglass board, thereby resulting in a reduced transmission of unwanted sound from the source of sound in the appliance. Further, it is known that the insertion of a reflecting sound barrier within the acoustical insulation also reduces the sound transmission through the insulation product. Reflecting sound barriers in the past have been made of paper and also of a thin layer of polymeric material, as well as of other materials such as asphalt. U.S. Pat. No. 5,094,318 to Maeda et al. discloses a sound absorption material for automobiles which includes a damping layer, which may act as a sound reflection barrier, a sound absorption layer which absorbs acoustical energy, and a surfacing materiel. The damping layer can be purely asphalt, or an asphalt modified with resins and polymers. The sound absorption layer can be a foamed material or a fibrous material such as a mineral fiber blanket. U.S. Pat. No. 5,965,851 to Herreman et al. discloses an accoustically insulated apparatus, such as a dishwasher or a washing machine. U.S. Pat. No. 5,965,851 to Herreann et al. is incorporated herein by reference in its entirety.